Rubber stopper placement and measurement

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Vials are small. The rubber stoppers that go in them, even smaller. But small things can lead to big problems for pharmaceutical manufacturers. Prior to capping and sealing, the rubber stopper in a vial must be seated properly. If it isn’t, costly product could be spilled, or sterility compromised. Genesis Machinery Products found that vision sensors work much better than photoelectric sensors when it comes to checking vials for raised stoppers. Vision sensors are less error-prone, more accurate, repeatable, and provide consistent results regardless of normal product-to-product inconsistencies. For pharmaceutical manufacturers, the new vision-based inspection system streamlines product changeovers, minimizes waste and provides data for better tracking of rejects. This article chronicles how Genesis developed the new inspection system for a major pharmaceutical manufacturer, and explores how the lessons learned from initial feasibility study through final system integration were applied to a new stand-alone raised stopper detection station.

Vision sensors check vials for raised stoppers

When it comes to packaging vaccines or other injectable medicines for patient treatment, pharmaceutical manufactures can ill afford to take risks. That’s why Genesis Machinery Products (Exton, PA), a manufacturer of high-tech pharmaceutical-grade packaging systems with expertise in seal integrity, switched from photoelectric sensors to vision sensors on a new vial inspection system that has been deployed at a leading pharmaceutical manufacturer.

The new system has helped the pharmaceutical company to improve the repeatability of the process, while minimizing downtime, changeover time and process waste. The system uses two In-Sight® vision systems from Cognex Corp. (Natick, MA; www.cognex.com), and provides 100% automatic inspection to detect raised stoppers on vials containing injectable liquid and lyophilized drug products prior to capping and sealing.

“If the rubber stopper on a vial is not seated properly before entering the capper, two things can go wrong,” said Genesis Senior Electrical Engineer Lou Cosentino. “The stopper could be pulled off and product spilled, or, the stopper could be pushed back into the vial and reseated. If this happens, there’s a chance that sterility could be compromised without detection.”

To assure seal integrity during the capping process, Genesis formerly used photo eyes to check for raised stoppers. The setup required an emitter to send out a very fine beam of light, and an opposing receiver. To work, the emitter and receiver must be mechanically aligned so good vials with properly seated stoppers pass under the beam, and vials with raised stoppers interrupt the beam. When an unseated stopper breaks the beam, the receiver signals the machine to stop so the flawed product can be removed.

The photo eye systems got the job done, according to Cosentino, but they were limited in three ways. First, the system wasn’t truly repeatable. Photo eye alignment depended on which operator set it up. Next, product changeovers were very time consuming. Photo eyes had to be mechanically adjusted each time the vial type changed. Finally, photo eyes would sometimes reject good product due to variations in vial height due to normal manufacturing inconsistencies.

“By using In-Sight vision sensors from Cognex, we’ve taken operator subjectivity out of the equation, tightened the tolerances significantly and improved the process,” says Cosentino. “The vision system isn’t fooled by normal vial inconsistencies, and changeovers now consist of selecting a new job via keyed entry on a touch screen.”

Tapping into vision

Having dabbled with machine vision before, Cosentino thought that vision technology might help improve the photo-eye based system. Cognex was contacted based on the pharmaceutical manufacturer’s recommendation, and a Cognex sales engineer scheduled an onsite evaluation at Genesis. “The sales engineer came in and set up an application demo on my desk, then spent some time going over what I would need to know to fine tune the system,” Cosentino explained.

To set up the application, the In-sight vision spreadsheet interface was used. The process involved selecting vision tools and parameters from drop-down menus. The vision spreadsheet then automatically generated tool results into worksheet cells, which were then linked together to set up the inspection measurements.

“By the time we finished, I felt very comfortable working with the spreadsheet, even with minimal experience. It was great to be able to configure machine vision the same way you use a normal spreadsheet, creating formulas and adding logic tools like ‘if/and’ statements. You can also use multiple vision tools and make reference to those tools just by clicking on the cell,” said Cosentino. “In-Sight was very easy to use, integrate, and set up time was minimal.”

In order to meet a very aggressive customer deadline, Genesis enlisted the consulting services of systems integrator Serview Inc. (West Berlin, NJ) to help bring the demo application up to the next level.

“There’s a big difference between inspecting a vial sitting on my desk and a developing a high-speed, rock-solid process application that will meet the demanding requirements of a pharmaceutical manufacturer,” Cosentino said. “With Serview’s help, it took only a few days for us to bridge that gap, and incorporate all the bells and whistles that were required. Serview was instrumental in developing a very robust program, and getting the system up and running. Plus, by the time they were done I felt very comfortable going back in to manipulate the program to optimize operation.”

Detecting raised stoppers

In order to provide full inspection coverage, the final specification required that Genesis integrate two In-Sight vision sensors into the custom-built machine. The vision sensors are arranged at right angles to each other to ensure that vials with stoppers that are cocked don’t proceed to the capping machine. “When a stopper is cocked, it may appear seated from one view, but not from the other,” Cosentino explained. “By using two vision sensors, we can ensure that the stopper is properly seated all the way around the circumference of the vial.”

During production, a feed screw spaces vials evenly on a conveyor and they are fed into a series of star wheels. The star wheels transport each vial, one at a time, in front of the two cameras at a rate of 600 per minute. Two red LED backlights located behind the vial inspection position help create optimal image contrast between the vial, stopper, and background to give the vision sensor the clearest possible view of the measurement area.

As a vial enters the field of view and is presented to the cameras, a trigger signal linked to the vision sensor through I/O is provided to initiate image acquisition. The vision sensor captures the image, and transfers it to the on-board vision processor for analysis where a variety of vision software tools are applied. First, the In-Sight PatFind® pattern matching tool compares each image to a pre-trained reference image of the vial and stopper. “It doesn’t matter if the vial height changes due to normal manufacturing variations,” said Cosentino. “PatFind simply looks for the geometric properties of the stopper within the image.”

Once this match has occurred, PatFind determines the exact X, Y, and theta position of the stopper and vial, then fixtures the various vision inspection tools at the right location to measure the distance between the top of the vial and the lip on the stopper. To do this, In-Sight Edge Detection tools are used to find the edges and then calculate the distance between points on each edge.

In addition to the visual information provided to the operator, each In-Sight vision sensor sends pass/fail information to the capping machine controller (PLC) through the I/O lines. A fail signal instructs the PLC to trigger a solenoid actuated reject star wheel mechanism to remove the flawed product from the process prior to capping. Good product proceeds through the capping and sealing machine, and then downstream to the manufacturer’s parenteral packaging area.

“The flexibility of PatFind completely eliminates the false rejects we used to get from photo eyes,” said Cosentino. “Moreover, PatFind allows the various edge and inspection tools to provide very accurate, consistent, and truly repeatable results.” From a hardware perspective, the In-Sight 5400 is a high-performance machine vision sensor with a die-cast aluminum housing, sealed M12 connectors, and protective lens cover that achieves an IP67 (NEMA 6) rating for dust and wash-down protection.

Operating the system

Each In-Sight vision sensor includes a built-in Ethernet 10/100BASE-T communications port, which connects through an Ethernet switch to a touch-panel computer from Advantech Automation Corp. (www.advantech.com). The Advantech TPC-1260 touch-panel computer features a 12.1-inch, high-luminance display and a low-power processor.

The TPC-1260 serves as a programming terminal and provides a visual display for the operator. During production, the machine operator can view the inspection image and a green or red pass/fail indicator light on the screen. For product changeovers, the operator selects new jobs via keyed entry on the touch screen.

Password protection prevents operators from making unauthorized changes, but when logged in as a programmer, the system can be easily tailored to meet the specific needs of the pharmaceutical manufacturer. For example, enabling the FTP function of the vision sensors allows users to have all images, or only failed images, saved to the touch panel computer’s hard drive for later review.

In addition, the touch-panel computer runs In-Sight Explorer software from Cognex that offers advanced tools to simplify application development and network administration. “In-Sight Explorer is intuitive and user friendly. One great benefit is that In-Sight Explorer allowed us to use saved images to modify the application off-line. We simply dragged and dropped them into the spreadsheet, then adjusted the parameters to optimize the performance of each vision tool,” said Cosentino. “I’ve worked with other vision systems, but Cognex is definitely much easier to use, understand and implement.”

Building on success

Machine vision has proven invaluable for this application, by allowing Genesis to raise the bar for quality assurance in the production environment. “Our strength is producing a quality seal at speed that not only looks good, but has high integrity,” Cosentino said. “The vision system allows us to advance the notion that when you buy our capper, you also buy our expertise in vial handling and seal integrity.”

The first system has been installed and is improving productivity by reducing time and labor costs for the pharmaceutical manufacturer. The system not only helps achieve a better quality product by providing 100% in-line inspection, but it improves accuracy and increases speed as well.

Some manufacturers prefer certain vendors for internal reasons, and in this instance, Genesis specified Cognex at the customer’s request. “We’ll work with whatever vendor our customer wants,” Cosentino explained. “However, after working with the In-Sight vision sensors, we’ve decided to use them on a new stand alone raised stopper detection station that we’ve just designed.”

The new system was introduced earlier this year in New York at InterPhex on April 26, and will be ideal for pharmaceutical manufacturers interested in retrofitting existing vial capping lines. Machine vision has enabled Genesis to build greater precision and flexibility into the standalone inspection station.

“With vision, we have the flexibility to easily incorporate other inspection tasks such as checking vial glass for defects, inspecting caps for placement and/or color. We can do OCV, 1D and 2D code reading,” Cosentino said. “By using Cognex vision to do multiple tasks, we can build on our expertise in high-speed vial handling and seal integrity.”